Pouch Type Case And Battery Pack Including The Same

ABSTRACT

The present invention relates to a pouch type case having trimming portions formed on both sides or four corners thereof and a battery pack including the same. The trimming portions are formed on the corners of the pouch type case such that the trimming portions are indented toward an electrode assembly accommodating part to reduce a unit area so as to increase pressure applied to unit cells when a battery pack is assembled, thereby facilitating assembling of the battery pack and increasing cell capacity per unit area. Furthermore, the unit cells can be fixed in the battery pack more stably. The pouch type case reduces the unit area so as to include a relatively large number of cells for pressure applied to the cells when the battery pack is assembled to thereby increase the cell capacity.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/845,829, filed Mar. 18, 2013, which is a continuation of U.S.application Ser. No. 13/186,849, filed Jul. 20, 2011, now U.S. Pat. No.8,426,057, which is a continuation of International Application No.PCT/KR2011/001927 filed on Mar. 21, 2011, which claims priority fromKorean Patent Application No. 10-2010-0024879 filed in Republic of Koreaon Mar. 19, 2010, the entire contents of which are incorporated hereinby reference.

TECHNICAL FIELD

The present invention relates to a pouch type case and a battery packincluding the same.

BACKGROUND OF THE INVENTION

With the development of portable electrode devices such as cellularphones, notebook computers, and camcorders, studies on rechargeablesecondary batteries are actively performed. Particularly, the lithiumsecondary battery operating at a voltage of approximately 3.6V hascapacity more than three times that of nickel-cadmium battery ornickel-metal hydride battery, which is widely used as a power supply ofportable electronic devices, and high energy density per unit weight,and thus utilization and study of the lithium secondary battery becomerapidly activated.

The lithium secondary battery can be classified into a liquidelectrolyte battery and a polymer electrolyte battery according toelectrolyte type. Generally, a battery using a liquid electrolyte isreferred to as lithium ion battery and a battery using a polymerelectrolyte is referred to as a lithium polymer battery. The lithiumsecondary battery can be manufactured in various forms, typically, incylindrical and square shapes. The lithium polymer battery, which iscurrently spotlighted, is manufactured in a deformable pouch shape suchthat its shape is freely changed. In addition, the lithium polymerbattery is advantageous to reduce the thicknesses and weights ofportable electronic devices since it light and has highs stability.

Recently, capacity increase and stability of the lithium secondarybattery become important issues as the lithium secondary battery is usedas a power supply of electric vehicles as well as various electrodedevices and studies on the capacity increase and stability of thelithium secondary battery are actively performed.

To increase the capacity of the lithium secondary battery, unit cellsmanufactured in a pouch type are stacked and electrically connected toassemble a battery pack to thereby provide a lithium secondary batteryhaving required capacity. The size of the battery pack cannot belimitlessly increased and light, compact and high-capacity battery packsare required.

Furthermore, since a battery pack having a specific unit area haselectrically connected unit battery cells, the battery pack may explodeif one of the unit battery cells is heated or short-circuited. Thisincreases a demand for battery packs having improved stability.

The shape of a unit battery cell 10 included in a conventional batterypack is illustrated in FIG. 1.

Referring to FIG. 1, the unit battery cell 10 includes an electrodeassembly 30 and a case 20 providing a space for accommodating theelectrode assembly 30. The electrode assembly 30 is composed of apositive plate, a negative plate and a separated interposed between thepositive plate and the negative plate. The electrode assembly 30 iswound into a shape of jelly-roll type with the positive plate, theseparator and the negative plate sequentially arranged or composed ofmultiple electrodes laminated in a stack structure.

Furthermore, the electrode assembly 30 includes a cathode lead 60 and ananode lead 70 electrically connected to each pole plate and exposed tothe outside of the sealed case 20. The case 20 is of pouch type that iscomposed of a thin metal film and an insulating film bonded to bothsides of the thin metal film and can be freely bent, distinguished froma cylindrical or square type case formed from a thick metal plate, tothereby accomplish compact electronic devices.

FIG. 2 is a partial enlarged view showing the top portion of the insideof the case 20 of the secondary battery shown in FIG. 1, where cathodetaps 40 are combined in a concentrated manner and connected to thecathode lead 60. FIG. 3 is a plan view of the secondary battery in anassembled state, shown in FIG. 1. Referring to FIGS. 2 and 3, thecathode taps 40 extended from a cathode current collector 41 andprojected are combined by welding, for example, and connected to thecathode lead 60 in the form of a welded portion. The cathode taps 40 ofthe welded portion are bent in an approximately V shape, and thus aconnecting portion of electrode taps and an electrode lead can bereferred to as a V-forming part. The cathode lead 60 is sealed by thebattery case 20 with the end 61, to which the cathode tap welded portionis connected, exposed to the outside of the case 20.

Since the cathode taps 40 are combined to form the welded portion, asdescribed above, the top end of the inside of the battery case 20 isspaced apart from the top end (or bottom end) of the electrode assembly30 by a predetermined distance. Accordingly, the distance L₁ between thetop end (or bottom end) of the electrode assembly 30 and the insulatingfilm is considerably long and a dead space irrespective of batterycapacity is generated around the welded portion of the cathode taps andthe cathode lead. In addition, if gas is generated in the battery pack,the generated gas can easily remain in the dead space.

The conventional pouch type secondary battery is inefficient since manydead spaces are generated in the battery due to its structure and, evenwhen external pressure applied to the secondary battery is increased torestrain generation of gas, it is difficult to restrain the generationof gas because a space where gas can remain exists inside the battery.

SUMMARY OF THE INVENTION

Accordingly, an aspect of the present invention is to solve the aboveproblems using a pouch type case capable of reducing an internal deadspace and provide a pouch type case for lithium secondary batteries,which can maximize space utilization when a battery pack structurerequiring holders is designed.

Another aspect of the present invention is to provide a battery packincluding the pouch type secondary battery having the above structure,in which unit cells can be stacked more stably.

There is provided a pouch type case having a space accommodating anelectrode assembly composed of a positive plate, a negative plate and aseparator interposed between the positive plate and the negative plateand a sealing part sealing up an upper case and a lower case, wherein aportion of the space and sealing part, which corresponds to at least oneof the left and right sides of an electrode lead projected to theoutside of the case, includes a trimming portion intended toward theelectrode assembly.

The trimming portion may be spaced apart from the electrode lead and thetop end of the electrode assembly by a distance corresponding to thewidth of the sealing part.

The trimming portion may be spaced apart from the electrode lead bylonger than 6 mm and shorter than the width of the electrode lead andspaced apart from the top end of the electrode assembly by longer than 3mm and shorter than the length of the electrode lead.

The trimming portion may have one of circular, oval, straight-line,rectangular, triangular, parabola and V shapes.

The pouch type case may include trimming portions respectively formed onthe corners of the case and the trimming portions have the same shape ordifferent shapes.

The electrode assembly may have an anode lead and a cathode leadprojected in different directions.

The anode lead and the cathode lead may be projected from one of ashorter side and a longer side of the electrode assembly.

Portions of the space and the sealing part, which correspond to the leftand right sides of the anode lead and the cathode lead, may respectivelyinclude trimming portions indented toward the electrode assembly.

The electrode assembly may have an anode lead and a cathode leadprojected in the same direction.

The direction in which the anode lead and the cathode lead are projectedmay correspond to one of the shorter side and longer side of theelectrode assembly.

Portions of the space and the sealing part and the space, whichcorrespond to both corners of the side from which the anode lead and thecathode lead are projected, may respectively include trimming portionsintended toward the electrode assembly.

A portion of the space and the sealing part between the anode lead andthe cathode lead may include a trimming portion intended toward theelectrode assembly.

The trimming portion may be spaced apart from the anode and cathodeleads and the top end of the electrode assembly by a distancecorresponding to the width of the sealing part.

The trimming portion may be formed in a parabola shape having a vertexcorresponding to a point spaced apart from the top end of the electrodeassembly by at least 3 mm.

The trimming portion may be formed in an inverted triangle having avertex corresponding to a point spaced apart from the top end of theelectrode assembly by at least 3 mm.

Portions of the space and the sealing part, which correspond to bothcorners of the side from which the anode and cathode leads areprojected, and a portion of the space and the sealing part between theanode and cathode leads may respectively include trimming portionsindented toward the electrode assembly.

The width of the sealing part including the trimming portion may bemaintained.

At least one side of the upper case and at least one side of the lowercase may be connected to each other

The upper case and the lower case may be separated from each other andrespectively have spaces accommodating the electrode assembly.

To achieve the above object, there is also provided a lithium secondarybattery comprising the pouch type case and the electrode assembly.

The electrode assembly may include a trimming portion having the sameshape as the trimming portion formed at the pouch type case at a portioncorresponding to the trimming portion formed at the case.

The electrode assembly may correspond to one of a stack & foldingelectrode assembly manufactured in such a manner that a bi-cell and afull-cell are arranged on a long separating film in an intersectingmanner and folded, a stack & folding electrode assembly manufactured insuch a manner that only the bi-cell is placed on the separating film andfolded, a stack & folding electrode assembly manufactured in such amanner that only the full-cell is placed on the separating film andfolded, a Z-shaped stack & folding electrode assembly manufactured byfolding the bi-cell or the full-cell using the separating film in azigzag direction, a stack & folding electrode assembly manufactured bycontinuously folding the bi-cell or full-cell in the same direction, anelectrode assembly manufactured in such a manner that an anode and acathode are arranged on a long separating film in an intersecting mannerand folded, a jelly-roll type electrode assembly manufactured by windinga positive plate, a separator and a negative plate, sequentiallyarranged, in one direction, and a stack-type electrode assembly.

Trimming portions may be previously formed at the upper case and thelower case of the pouch type case, and then the sealing part may besealed through thermal bonding.

To achieve the above object, there is also provided a battery packcomprising the lithium secondary battery.

The battery pack may include a holder arranged on the trimming portionsformed at the pouch type case of the lithium secondary battery.

The cross-sectional shape of the holder may correspond to the shape ofthe trimming portions formed at the pouch type case.

The battery pack may be used as a power supply of amedium-and-large-size device.

The medium-and-large-size device may correspond to a power tool, anelectric vehicle such as a hybrid electric vehicle and a plug-in hybridelectric vehicle, an electric two-wheeled vehicle including E-bike andE-scooter, an electric golf cart, an electric truck, an electriccommercial vehicle, or an electric power storage system.

The pouch type case according to the present invention can reduce theinternal dead space to improve space utilization and fix a battery packmore stably when a battery pack structure requiring a holder isdesigned. That is, the stability and space utilization of the batterycase can be maximized. Furthermore, the decrease in the internal deadspace of the battery reduces a space where gas may remain in caseemergency. In addition, the pouch type case has high internal pressureso as to rapidly ventilate gas and restrain generation of additionalgas.

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an exploded perspective view of a general structure of aconventional pouch type secondary battery;

FIG. 2 is a partial enlarged view illustrating the top portion of theinside of a battery case of the secondary battery shown in FIG. 1, wherecathode taps are combined in a concentrated manner and connected to acathode lead;

FIG. 3 is a plan view of the secondary battery shown in FIG. 1 whenassembled;

FIG. 4 is a plan view of a conventional pouch type secondary batteryhaving electrode leads projected in two directions;

FIGS. 5 through 9 are plan views of secondary batteries having electrodeleads projected in one direction according to embodiments of the presentinvention;

FIG. 10 is an exploded perspective view corresponding to the view ofFIG. 6 and showing a pouch including upper and lower cases connectedwith each other through one side thereof and having three sealed sides;

FIG. 11 is an exploded perspective view corresponding to the view ofFIG. 6 and showing a pouch including upper and lower cases separatedfrom each other and having four sealed sides;

FIGS. 12 and 13 are plan views of secondary batteries having electrodeleads projected in two directions according to embodiments of thepresent invention; and

FIGS. 14, 15 and 16 are perspective views of battery packs including thepouch type case according to the present invention and a holder.

DETAILED DESCRIPTION

A pouch type case according to an embodiment of the present inventionincludes a space accommodating an electrode assembly composed of apositive plate, a negative plate and a separator interposed between thepositive and negative plates and a sealing part sealing up an upper caseand a lower case, in which a portion of the space and the sealing part,which corresponds to at least one of left and right sides of anelectrode lead projected to the outside of the case, is trimmed to beindented toward the electrode assembly so as to minimize an internaldead space of a battery using the pouch type case.

As described above, the dead space in the electrode assembly isgenerated in a region where an electrode lead is formed in order to forma welded portion of electrode taps and the electrode lead.

Accordingly, to minimize the dead space, portions of the pouch type caseaccording to the present invention other than a portion corresponding toa minimum region for forming the welded portion of the electrode leadand the electrode taps around the electrode lead are trimmed to beindented toward the electrode assembly.

The pouch type case having a minimized internal dead space according tothe present invention has battery internal pressure higher than that ofa conventional pouch type case having the same size, and thus the pouchtype case according to the present invention can further restrain thegeneration of gas. In addition, when a battery pack is assembled usingsecondary batteries including the aforementioned pouch type case as unitcells, the battery pack can contain a larger number of cells for thepressure applied to the battery pack when assembled. Moreover, a holdercan be inserted into trimming portions so as to improve stability.

The pouch type case according to the present invention may haveelectrode leads projected in different directions. Here, the electrodeleads may be projected from a longer side as well as a shorter side of aunit battery cell.

When the pouch type case includes the above electrode assembly, atrimming portion can be formed at one of the left and right sides ofeach electrode lead and, desirably, trimming portions can berespectively formed at the left and right sides of each electrode lead.When the trimming portions are respectively formed at the left and rightsides of each electrode lead, the internal dead space of the battery canbe further minimized and generation of gas can be effectivelyrestrained.

If the electrode assembly has a single anode lead and a single cathodelead, trimming portions are respectively formed on four corners of thepouch type battery case such that the trimming portions are intendedtoward the electrode assembly.

Furthermore, the pouch type case according to the present invention mayhave electrode leads projected in the same direction. Here, theelectrode leads may be projected from a longer side as well as a shorterside of the unit battery cell.

In this case, trimming portions may be respectively formed on bothcorners of the sealing side from which the electrode leads areprojected.

That is, in the case of the electrode assembly having a single anodelead and a single cathode lead projected in the same direction, thepouch type case may have trimming portions respectively formed on bothcorners of the side from which the electrode leads are projected.

The shape or size of the trimming portion is not limited and may dependon battery capacity or size. However, the trimming portion is requiredto be spaced apart from the electrode assembly inserted into the pouchto reduce dielectric breakdown, which depends on the battery size. In anembodiment of the present invention, the trimming portion may be spacedapart from the top end of the electrode assembly by at least 3 mm.

Furthermore, it is desirable to space the trimming portion from theelectrode lead projected to the outside of the case by a distancecorresponding to the width of the sealing part. The distance between thetrimming portion and the electrode lead may depend on the battery sizesince the width of the sealing part depends on the battery size. In anembodiment of the present invention, the trimming portion is spacedapart from the electrode lead by at least 6 mm based on the sealingwidth (6 mm) of the pouch type case.

Although the upper limit of the spacing distance is not limited, thetrimming portion may be spaced apart from the electrode lead by adistance in the range of 6 mm to the width of the electrode lead andspaced apart from the top end of the electrode assembly by a distance inthe range of 3 mm to the vertical length of the electrode lead in anembodiment of the present invention.

If the trimming portion is indented by a distance exceeding the minimumspacing distance, it may be difficult to protect the electrode assemblyand the electrode taps from external impact and a space in whichelectrolyte can remain is too small to cause the function of the batteryto be affected.

If the trimming portion of the pouch type case according to the presentinvention is designed to be spaced apart from the electrode assembly andelectrode lead by appropriate distances, as described above, the shapeor size of the trimming portion is not limited and can depend on thebattery capacity or size and the trimming portion can be formed invarious shapes including circular, oval, rectangular and straight-lineshapes.

In the case of the pouch type battery case having electrode leadsprojected in the same direction, a trimming portion may be formed, beingintended toward the electrode assembly, at a portion of the space andthe sealing part between the electrode leads so as to minimize theinternal dead space of the battery.

The shape or size of the trimming portion formed between the electrodeleads is not limited since it depends on the battery capacity or size.To protect the electrode assembly and electrode taps from externalimpacts and secure a space where electrolyte can remain, the trimmingportion is required to be spaced apart from the electrode assemblyinserted into the pouch by a predetermined distance so as to reducedielectric breakdown, which depends on the battery size. The trimmingportion may be spaced apart from the top end of the electrode assemblyby at least 3 mm in an embodiment of the present invention. Furthermore,the trimming portion may be spaced apart from the electrode leadprojected to the outside of the case by a distance corresponding to thewidth of the sealing part. Since the width of the sealing part maydepend on the battery size, the distance between the trimming portionand the electrode lead may also depend on the battery size. In anembodiment of the present invention, the trimming portion may be formedsuch that the trimming portion is spaced apart from the electrode leadby at least 6 mm based on the sealing width (6 mm) of the pouch. If thetrimming portion is indented by a distance exceeding the minimum spacingdistance, it may be difficult to protect the electrode assembly and theelectrode taps from external impacts and the function of the battery maybe affected since a space where electrolyte is very small. Accordingly,in a preferred embodiment of the present invention, the trimming portionbetween the electrode leads may be formed in a parabola having a vertexcorresponding to a point spaced apart from the top end of the electrodeassembly by at least 3 mm. Otherwise, the trimming portion may be formedin a semicircle, an oval or an inverted triangle,

The pouch type case may have an upper case and a lower case separatedfrom each other or connected with each other through at least one sidethereof.

Furthermore, the space accommodating the electrode assembly may beformed in one of the upper and lower cases or formed in both the upperand lower cases.

FIG. 10 is an exploded perspective view of a pouch type case 220including upper and lower cases connected with each other through oneside thereof and having three sealed sides and FIG. 11 is an explodedperspective view of a pouch type case having an upper case 220 b and alower case 220 a separated from each other and an electrode assemblyaccommodating space formed in both the upper and lower cases 220 b and220 a (double cup structure). In the pouch type case shown in FIG. 11,all the four sides of the case are sealed.

A method of manufacturing the pouch type battery case according to thepresent invention is not limited and may use the conventionalmanufacturing method. Specifically, the above-described trimming portionis previously formed at the pouch type case such that the internal deadspace of the battery using the pouch type case is minimized inconsideration of the capacity, size and purpose of the battery, theelectrode assembly is mounted in the space for accommodating theelectrode assembly, and then the sealing part is sealed through thermalbonding to produce a unit battery cell.

The electrode assembly includes the positive plate, the negative plateand the separator interposed between the positive plate and the negativeplate.

The positive plate includes a positive current collector formed from astrip-shaped sheet metal and a positive active material layer coated onat least one side of the positive current collector. The positivecurrent collector may be an aluminum sheet having high conductivity andthe positive active material layer is not limited and may be acomposition of lithium oxide, binder, plasticizer, and conductivematerial. The cathode lead is attached to a non-coated portion of thepositive plate.

The negative plate includes a negative current collector formed from astrip-shaped sheet metal and a negative active material layer coated onat least one side of the negative current collector.

The negative plate may be sheet copper having high conductivity and thenegative active material layer may be a composition of a negative activematerial such as carbon, binder, plasticizer and conductive material.The anode lead is attached to a non-coated portion of the negativeplate.

The anode lead and the cathode lead are electrically connected to thesurfaces of positive and negative non-coated portions. To achieve this,the anode lead and the cathode lead are electrically bonded to thepositive and negative non-coated portions through welding such as laserwelding or ultrasonic welding or using a conductive adhesive.

The electrode assembly included in the pouch type case according to thepresent invention is not limited to a specific shape and may havevarious shapes. Examples of the electrode assembly can include a stack &folding electrode assembly constructed in such a manner that a bi-celland a full-cell, stack-type unit cells of different types, are arrangedin an intersecting manner and wound by a long separating film, a stack &folding electrode assembly including stack-type unit cells of the sametypes, a Z-shaped stack & folding electrode assembly having stack-typeunit cells wound by a separating film and folded in a zigzag direction,a stack & folding electrode assembly having stack-type unit cellscontinuously wound in the same direction, an electrode assemblyconstructed in such a manner that an anode and a cathode are alternatelyarranged on a separating film and continuously wound, a Z-shapedelectrode assembly constructed in such a manner that an anode and acathode are alternately arranged on a separating film and wound in azigzag direction, a general stack-type electrode assembly, and ajelly-roll type electrode assembly constructed in such a manner that apositive plate, a separator, and a negative plate are sequentiallyarranged and wound in one direction.

When the pouch type case accommodates a stack-type electrode assembly inan embodiment of the present invention, a negative pole plate, apositive pole plate and a separator of the stack-type electrode assemblymay have trimming portions corresponding to the trimming portions of thepouch type case.

In the pouch type case according to the present invention, oppositefaces of the upper and lower cases may be formed from a film havingthermal adhesion and a plurality of films of other materials may besequentially stacked and combined. Here, the film of the upper and lowercases may be composed of a polyolefin resin film having thermal adhesionand functioning as a sealing material, a base for maintaining themechanical strength of the case, an aluminum film functioning as abarrier against moisture and oxygen, and a nylon film serving as a baseand a protection layer.

The outer shape of the combined upper and lower cases maintains arectangle to correspond to the outer shape of the battery such that thevolume of the outer shape of the combined upper and lower cases can beminimized.

The upper and lower cases may be in contact with each other through ateast one side thereof and other sides thereof may be open.

One of the upper and lower cases may have the space accommodating theelectrode assembly and the sealing part is formed along the edge of thespace. Furthermore, the space accommodating the electrode assembly maybe formed in both the upper and lower cases.

The sealing part means a portion of the case, which is sealed throughthermal bonding after the electrode assembly, is mounted in the space.

The electrode assembly having the above structure may be wound in onedirection with the positive plate, the separator and the negative platesequentially arranged, that is, in a jelly-roll-type structure.

The jelly-roll type electrode assembly manufactured as above hassemiconductor polymer electrolyte formed on the separator made of apolymer with flexibility, for example, polyethylene, and thus thejelly-roll type assembly can operate as a lithium secondary batterywithout requiring additional electrolyte to be injected thereto tothereby minimize the internal dead space of the battery.

The jelly-roll type electrode assembly is mounted in the upper or lowercase in which the space is prepared. Here, the ends of the anode leadand the cathode lead electrically connected to pole plates of theelectrode assembly are projected to the outside of the sealed case.

After the electrode assembly is mounted in the space, predetermined heatand pressure are applied to the sealing part formed along the edge ofthe space to seal up the case. Here, the sealing part is integrated withthe case and extended from the case along the edge of the space andmaintains a predetermined width.

It is desirable to maintain the predetermined width of the sealing partin a portion of the sealing part, which has a trimming portion. Theportion of the sealing part around an electrode lead may have a thickerwidth such that the portion around the electrode lead can be sealed moresecurely.

The present invention provides a battery pack including the pouch typecast having indented portions.

The battery pack is constructed in such a manner that unit cellsincluding the pouch type case according to the present invention arearranged in a module case and packaged. When the battery pack isassembled, relatively high pressure is applied to the battery pack forapplied specific pressure, and thus the unit cells become compact sothat a larger number of unit cells can be packed in the module casehaving a specific area, thereby providing a large-capacity battery pack.

The unit cells may be sequentially stacked in the module case orconnected in parallel in the module case.

The unit cells stacked or arranged in parallel in the module case mustbe securely fixed through a method such as bonding to be prevented fromshaking or short-circuiting when the battery pack is used.

The battery pack according to the present invention arranges a holder onthe trimming portions formed at the unit cells stacked or connected inparallel in the module cast to stably fix the unit cells in the modulecase, thereby maximizing the stability of the unit cells.

In this case, the shape and size of the holder may correspond to theshape and size of the trimming portions formed at the unit cells suchthat the holder can be mounted on the trimming portions of the unitcells more stably. The holder can securely fix the unit cells in themodule case to remarkably improve the stability of the battery pack.

The battery pack according to the present invention can be used not onlyas a power supply of a small-size device but also as amedium-and-large-size device including a plurality of battery cells.

Examples of the medium-and-large-size device can include power tools,electric vehicles including a hybrid electric vehicle and a plug-inhybrid electric vehicle, two-wheeled vehicles including E-bike andE-scooter, electric golf carts, electric trucks, electric commercialvehicles and power storage systems. However, the medium-and-large-sizedevice is not limited thereto.

The present invention will now be described more fully with reference tothe accompanying drawings, in which exemplary embodiments of theinvention are shown. The invention may, however, be embodied in manydifferent forms and should not be construed as being limited to theembodiments set forth herein.

FIGS. 5 through 11 are plan views of a pouch type battery case 220according to embodiments of the present invention, which has electrodeleads projected in the same direction.

The pouch type battery case 220 may have a trimming portion 234 formedon at least one of the left and right sides of the electrode leads 25and 27 and intended toward an electrode assembly 21 so as to minimize adead space formed around the electrode leads 25 and 27.

The size and shape of the trimming portion are not limited and thetrimming portion can be formed in various shapes such as a straight-lineshape (shown in FIG. 5), a curved shape (shown in FIG. 6) and arectangular shape (shown in FIG. 7). However, it is desirable that thetrimming portion is spaced apart from the top end of the electrodeassembly 21 by at least 3 mm and spaced apart from the electrode leads25 and 27 by at least the width of the sealing part in order toeffectively protect the electrode leads 25 and 27 and the electrodeassembly 21 from external impacts.

Referring to FIGS. 8 and 9, a trimming portion may be formed between theelectrode leads 25 and 27 projected in parallel. The shape of thetrimming portion is not limited as long as the aforementioned minimumspacing distances are maintained. While the trimming portion has acurved shape or V shape in the embodiments shown in FIGS. 8 and 9, theshape of the trimming portion is not limited thereto.

When the electrode leads are projected in two directions, it isdesirable to respectively form trimming portions on the four corners ofthe pouch type battery case, as shown in FIGS. 12 and 13. However, thepresent invention is not limited to the embodiments shown in FIGS. 12and 13.

FIGS. 14, 15 and 16 are perspective views of battery packs having unitbattery cells 210 including the pouch type battery case 220 according tothe present invention. Each battery pack may include a holder 400 havinga cross-sectional shape corresponding to the shape of trimming portionformed at the pouch type battery case included therein. The holder 400may be arranged in a module case 300.

The shape and number of the holders 400 may depend on the positions ofthe trimming portions formed at the pouch type battery case and are notlimited to the above embodiments.

While the present invention has been particularly shown in and describedwith reference to exemplary embodiments thereof, it will be understoodby those of ordinary skill in the art that various changes in form anddetails may be made therein without departing the spirit and scope ofthe present invention as defined by the following claims.

1. A secondary battery comprising: an electrode assembly includingelectrode leads projected in a first direction; and a pouch type casecomprising a space for accommodating the electrode assembly, and asealing part sealing up an upper case and a lower case, wherein aportion of the space and sealing part includes trimming portionsintended toward the electrode assembly, wherein the trimming portionsinclude: a first trimming portion disposed between electrode leads; anda pair of second trimming portions disposed on opposite sides to eachother with respect to the electrode leads, and respectively disposedadjacent to a corner of the electrode assembly, and wherein, in thefirst direction, a distance between the second trimming portion and theelectrode assembly is greater than or equal to a distance between thefirst trimming portion and the electrode assembly.
 2. The secondarybattery of claim 1, wherein the second trimming portion defines a cornerof the pouch type case.
 3. (canceled)
 4. The secondary battery of claim1, wherein the trimming portion has one of circular, oval,straight-line, rectangular, triangular, parabola and V shapes.
 5. Thesecondary battery of claim 1, wherein the pair of second trimmingportions have shapes symmetrical to each other. 6-13. (canceled)
 14. Thesecondary battery of claim 1, wherein the first trimming portion isformed in a parabola shape having a vertex corresponding to a pointspaced apart from the electrode assembly by at least 3 mm.
 15. Thesecondary batter of claim 1, wherein the first trimming portion isformed in an inverted triangle having a vertex corresponding to a pointspaced apart from the electrode assembly by at least 3 mm. 16.(canceled)
 17. (canceled)
 18. The secondary battery of claim 1, whereinat least one side of the upper case and at least one side of the lowercase are connected to each other.
 19. The secondary battery of claim 1,wherein the upper case and the lower case are separated from each otherand respectively have spaces accommodating the electrode assembly.
 20. Abattery pack comprising the secondary battery according to claim 1.